Water quality and limnology of Korean reservoirs

Reservoirs are the predominant type of lentic ecosystem in Korea, and they account for a considerable proportion (similar to 59%) of the agricultural water uses. There are 18,797 reservoirs in Korea; most (similar to 90%) are small (storage capacity <1,000,000 m(3)), and most provide irrigation water for paddy farming. Characteristics of Korean agricultural reservoirs are high watershed-reservoir area ratios, shallow depth, unstable hydrodynamics, and eutrophic conditions. Many agricultural reservoirs are relatively old; 54% of all reservoirs were constructed more than 50 years ago. As a result, they have a considerable amount of organic matter accumulation on the sediment, which may contribute to the internal loading of nutrients. Deterioration of water quality and ecosystem health, resulting from cultural eutrophication and harmful algal blooms, are common problems in most Korean agricultural reservoirs. Environmental considerations about reservoirs, especially their ecological functions, have largely been ignored in past management plans. Limnology, the multidisciplinary study of lakes and reservoirs, can provide conceptual models of reservoirs and fundamental information needed to determine causes and potential solutions for environmental stresses. Problems prevailing in Korean reservoirs, such as cultural eutrophication and harmful algal blooms, are complicated ecosystem-level phenomena with many factors interacting with each other. Thus, limnological understanding is a prerequisite to identifying sound solutions and to making wise judgments about reservoir management and restoration. Cooperation with other related disciplines is necessary to establish the proper management plans and applications. Also, international cooperation is suggested to solve environmental problems in agricultural reservoirs, particularly among the countries with similar agricultural practices, climate, geology, and water uses.